# I say to you

Here "you" is plural. Jesus was speaking to the religious leaders who had rejected him.

# the kingdom of God will be taken away from you and will be given to a nation that produces its fruits

"God will take his kingdom away from you and will give it to a nation that produces the kingdom's fruits" or "God will reject you, and he will be king over people from other nations that produce the kingdom's fruits" 

# that produces its fruits

"that produces good results"